Magnetic resonance imaging of intracranial venous angiomas

DEVELOPMENTAL VENOUS ANOMALIES

DEVELOPMENTAL VENOUS ANOMALIES (DVAs), formerly known as venous angiomas, have become the most frequently diagnosed intracranial vascular malformation. DVAs are currently considered congenital cerebrovascular anomalies with mature venous walls that lack arterial or capillary elements. They are composed of radially arranged medullary veins, which converge in an enlarged transcortical or subependymal collector vein, and have characteristic appearances (caput medusae) on magnetic resonance imaging and angiography. DVAs were once thought to be rare lesions with substantial potential for intracerebral hemorrhage and considerable morbidity. The prevalence of incidental and asymptomatic DVAs has been more apparent since the advent of magnetic resonance imaging; recent cohort studies have challenged the once-held view of isolated DVAs as the cause of major neurological complications. The previously reported high incidence of intracerebral hemorrhage associated with DVAs is currently attributed to coexistent, angiographically occult cavernous malformations. Some patients may still have noteworthy neurological morbidity or die as a result of acute infarction or hemorrhage directly attributed to DVA thrombosis. DVAs can coexist with cavernous malformations and arteriovenous malformations. Such combination or transitional forms of malformations might suggest common pathways in pathogenesis. Recent data support a key role for DVAs in the pathogenesis of mixed vascular malformations.

Pathomechanisms of Symptomatic Developmental Venous Anomalies

Background and Purpose— Although it is generally accepted that developmental venous anomalies (DVAs) are benign vascular malformations, over the past years, we have seen patients with symptomatic DVAs. Therefore, we performed a retrospective study and a literature study to review how, when, and why DVAs can become clinically significant.

Methods— Charts and angiographic films of 17 patients with DVAs whose 18 vascular symptoms could be attributed to a DVA were selected from a neurovascular databank of our hospital. MRI had to be available to rule out any other associated disease. In the literature, 51 cases of well-documented symptomatic DVAs were found. Pathomechanisms were divided into mechanical and flow-related causes.

Results— Mechanical (obstructive or compressive) pathomechanisms accounted for 14 of 69 symptomatic patients resulting in hydrocephalus or nerve compression syndromes. Flow-related pathomechanisms (49 of 69 patients) could be subdivided into complications resulting from an increase of flow into the DVA (owing to an arteriovenous shunt using the DVA as the drainage route; n=19) or a decrease of outflow (n=26) or a remote shunt with increased venous pressure (n=4) leading to symptoms of venous congestion. In 6 cases, no specific pathomechanisms were detected.

Conclusions— Although DVAs should be considered benign, under rare circumstances, they can be symptomatic. DVAs, as extreme variations of normal venous drainage, may represent a more fragile venous drainage system that can be more easily affected by in- and outflow alterations. The integrity of the DVA needs to be preserved irrespective of the treatment that should be tailored to the specific pathomechanism.

Cavernous haemangiomas (angiomas) of the brain

This paper highlights the importance of cavernous haemangiomas as clinically significant lesions and the role of imaging, particularly MRI, in suggesting the diagnosis. An understanding of the pathology of these lesions helps to explain the features demonstrated by imaging techniques.

Intracranial developmental venous anomalies: diagnosis using CT angiography

Four cases in which the diagnosis of developmental venous anomaly (DVA) was made using CT angiography are illustrated. The diagnosis of DVA was confirmed by either MR (all cases), digital subtraction angiography (two cases), or both (one case). This is the first report, to our knowledge, of the CT angiographic appearance of DVA.

Cerebral venous angiomas associated with hemorrhagic lesions. Their MRI manifestations

Using two 1.5-T magnetic resonance (MR) scanners, 82 venous angiomas (VAs) were imaged. There were 13 (16%) VAs associated with hemorrhagic lesions. Ten of the 13 hemorrhagic lesions were considered hematomas in the subacute or chronic stage, caused by VAs or coexisting cavernous hemangiomas. Two of the 13 were subacute intracerebral hematomas; the remaining one was a sequela of a hemorrhagic venous infarct. After analysis of our data, it was concluded that infratentorial VAs and deeply draining supratentorial VAs in relatively young adults, especially females, are relatively frequently associated with intracerebral hemorrhagic lesions. MR imaging proved useful for diagnosing VAs and associated hemorrhagic lesions.

The occipitotemporal vein: a cadaver, MRI and CT study

The author studied a superficial temporal vein running anteroposteriorly within the occipitotemporal sulcus, the "occipitotemporal vein", which, when prominent, could be thought to simulate a "venous angioma" on MRI. A cadaver (n = 50), MRI (n = 200), and CT (n = 50) study was undertaken to examine the incidence, detectability, size, location, and drainage of the occipitotemporal vein. It was an approximately 3 mm wide, 2-5 cm long structure. It was present in 83% of the cadavers (52% bilaterally), and clearly identifiable on 73% of the MRI (43% bilaterally), and 8% of the CT studies. In 18% of the cadavers the vein was totally absent, and it was not seen in 27% of the MRI examinations. The occipitotemporal vein can be distinguished from a venous angioma by its particular location and course, and by lack of intraluminal bright signal on spin-echo T2-weighted and/or contrast-enhanced T1-weighted images. In addition, venous angiomas are usually intraparenchymal, whereas the occipitotemporal vein is a superficial vessel.

MR imaging and angiography of cerebral venous angiomas associated with brain tumors

MR study of 6 patients with concurrent venous angioma and brain tumor revealed that in 2 of the 6 cases, the draining vein of the venous angioma was located near to the tumor and was displaced by the tumor. Two of the 6 venous angiomas were too small to visualize prior to contrast enhancement, but could be detected following administration of Gd-DTPA. Angiography was required for definitive diagnosis of the venous angiomas. When a venous angioma is suspected or is detected incidentally, especially when very near a brain tumor, angiography should be considered before performing surgery to avoid surgical complications. Otherwise, ligation of the vein draining the venous angioma may lead to venous infarction.